Field of Invention
The present invention relates to a field of electromagnetic functional device technology, focusing on a quickly dynamic functional device for a terahertz band.
Description of Related Arts
As one of the key components of the terahertz (THz) communication system, a THz dynamic functional device, namely terahertz external modulator, has becomes the focus of research in the field of THz science and technology. Since terahertz band functional devices required size in micron or nanometer scale, which means microwave and infrared bands devices cannot be applied directly. Therefore, since 2004, Nature/Science and the other top international scientific journals have published many articles about terahertz external modulators, covering a range of combining Si, GaAs, phase-transition, Graphene material systems with metamaterial. By applying external excitation such as temperature changes, light, and electrical field, the THz wave is modulated.
In recent years, with the development of semiconductor materials and technology, High Electron Mobility Transistor (HEMT) have shown excellent performance, and have been successfully applied to detectors, amplifiers, and other areas. HEMT is a novel field effect transistor which applies 2-dimensional electrons gas (2-DEG) in modulation doped heterostructures to work. In 1978, R. Dingle firstly observed high electron mobility. In 1980, Fujitsu developed a HEMT and successfully used it in low noise amplifier. As the third generation of wide bandgap semiconductor material, GaN has not only wide band gap, but also a large thermal conductivity, high electron saturation rate, strong breakdown field and good thermal stability, etc. Therefore, in the preparation of the high-speed functional devices, GaN-based HEMT material has great advantages.
Metamaterial is a kind of artificial electromagnetic array structure, which is made from assemblies of specific geometry resonance units with periodic or aperiodic patterns. The artificial designed structures give them their smart properties capable of manipulating electromagnetic waves to achieve benefits that go beyond what is possible with conventional materials. With the development of modern micro-fabrication techniques, metamaterials played a huge role in the development of passive functional devices, and have developed a variety of related functions devices in millimeter wave, THz, and optical band.